Charging batteries with both a UPS AND solar PV!?

[bennelson]

Hey Guys,

I have a question for you.

I have a bank of batteries running at 48V. I am charging them with a 48V UPS (uninterruptable power supply.)

I have some PV. Very basic, just several amorphous panels - 12V/15w from the 45 watt solar panel set available at Harbor Freight.

I have a Xantrex solar charge controller that will run at 12/24/48V.

What I would like to do is be able to charge the batteries from either the UPS (which can charge at up to 10 amps) OR from the solar (which would be a much lower amp rate, but FROM THE SUN!)

My question is, how do I do this? Would I need a manual switch? Could I simply just have BOTH hooked up at the same time?

I have noticed that the UPS needs to be "pre-charged" before connecting a battery pack to it, similar to what you do in an electric car with the motor controller. If I had to manually switch back and forth between solar charging and UPS charging, that may play into it.

I have two sets of batteries. One is AGMs on a rack near the UPS. The other is AGMs in my electric motorcycle (also running at 48V). I want to be able to charge the motorcycle with this system, and after that's charged, charge the stationary set of batteries. I would have one or the other set of batteries connected to the charging system at all times.

I want to be able to USE the batteries by either driving the electric motorcycle OR feeding the power back through the UPS to power my garage or house in event of a blackout.

I already have it all figured out and working for the UPS blackout protection, and have 50 amp Anderson disconnects to be able to easily connect either the cycle or the stationary battery pack to the UPS. I just want to figure how to integrate a little bit of solar power.

 

[amberwolf]

Well, if you can up the voltage on the UPS and Solar outputs by the difference in voltage this would cause, you could put diodes in series with each source (so they can't backfeed each other) and hook them both up to the batteries simultaneously.

The solar might already have a diode on it's output to prevent the battery from backfeeding into the charge controller, but if the charge controller includes the inverter (or the switching stuff to route it to the inverter) then it may not have any diode in there; you'd have to either check the circuitry or ask Xantrex.

The UPS won't have any diode in there, as it is designed to run as the inverter when it is not running as the charger. Putting a diode in place means that it will not run as an inverter from the batteries, unless you bypass the diode. That could be done manually or automatically, with something to switch a short into place across the diode. (switch, relay, etc.)